Membranes of immature neurons which are devoid of synaptic input are selectively sensitive only to neurotransmitters to which they will eventually be receiving synaptic input. In the peripheral nervous system it appears that synapse formation onto a muscle fiber cannot occur in the absence of the response of the postsynaptic membrane to the neurotransmitter. The role of receptor sensitivity in influencing the processes of snyaptogenesis in the central nervous system has not been examined. The studies outlined in this proposal will assess the long-term effects of chronic administration during central nervous system development of the dopamine receptor blocking agent, haloperidol, using behavioral, pharmacological and neurochemical approaches.